An image special effect apparatus in a related art includes frame memory 1702 and a read address computation section 1709 for computing an image special effect read address 1708 from a sequential write address 1705, as shown in FIG. 17. FIG. 17 is a block diagram of the image special effect apparatus in the related art.
For an input image 1701 sequentially written into the frame memory 1702 according to the sequential write address 1705, an output image 1703 is read from the frame memory 1702 according to the image special effect read address 1708 computed in the image special effect read address computation section 1709, whereby various video effects of page turn effect, ball effect, etc., are applied to the image.
A calculation method of a read address in a display screen horizontal direction when the page turn effect is realized in the image special effect apparatus in the related art is to calculate Xeffect shown as in the following expression for each of a lower flat face part 215, a lower curved face part 216, an upper curved face part 211, and an upper flat face part 212 from a write address x in a sequential display screen horizontal direction X213 as shown in FIG. 18. In FIG. 18, Z214 denotes an eye point direction 214 (z axis), R202 denotes an effect radius 202 (r), and θz240 denotes the angle between the eye point direction Z214 and a normal vector. FIG. 18 is a drawing to describe the horizontal coordinate calculation specifications in the image special effect apparatus in the related art.    (Lower flat face part 215) Xeffect=x    (Lower curved face part 216) Xeffect=rθz=r×arcsin(x/r)    (Upper curved face part 211) Xeffect=πr/2−rθz=πr/2−r×arcsin(x/r)    (Upper flat face part 212) Xeffect=πr/2−x
A read address calculation method in a display screen vertical direction is to calculate Yeffect shown as in the following expression for each of the lower flat face part 215, the lower curved face part 216, the upper curved face part 211, and the upper flat face part 212 from a write address y in a sequential display screen vertical direction Y222 as shown in FIG. 19. A231 in FIG. 19 denotes an upper face move amount. FIG. 19 is a drawing to describe the vertical coordinate calculation specifications in the image special effect apparatus in the related art.